Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 577
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Full Record for Micrograph 577

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Micrograph no
577
Brief description
Injection-moulded polypropylene (PP) hinge
Keywords
alignment, birefringence Link to MATTER Glossary entry for birefringence, hinge, injection moulding Link to MATTER Glossary entry for injection moulding, polymer Link to MATTER Glossary entry for polymer, polypropylene (PP)
Categories
Polymer
System
Polypropylene (PP)
Composition
Not specified
Standard codes
Reaction
Processing
Polypropylene flows through a constriction in the mould to form a flexible 'hinge' in the component
Applications
Polypropylene has good resistance to chemicals and to fatigue. It is widely used in food packaging in the form of rigid tubs, lids and screw-tops as well as in flexible films.
Sample preparation
Technique
Cross-polarised light microscopy
Length bar
1.4 mm
Further information
The colours in the image are the result of birefringence and relate to the residual strain in the polypropylene. The pattern of strain is indicative of the flow of material during the injection process and reveals the molecular alignment in the constriction which constitutes a hinge. The aligned molecules provide a fatigue resistant, flexible joint. A sprue which has been cut off is also visible in the top left-hand corner of the image.
Contributor
J A Curran
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International